Sulfuric acid is an important catalyst widely used in various chemical reactions. However, sulfuric acid has a large number of problems. For example, sulfuric acid is generally required in large amounts, causes apparatus corrosion, and requires the steps of separating, collecting, purifying and reusing sulfuric acid from the product after the reaction, the steps of neutralizing, the sulfuric acid remaining in the product, removing and discarding the salt generated thereby, and treating the wastewater treatment, and the like, and further, these steps require a lot of energy. In addition, while hydrogen fluoride is known as a liquid acid catalyst with comparatively fewer waste problems, problems thereof are that hydrogen fluoride is so corrosive that a special alloy is required for a reaction apparatus, and that hydrogen fluoride is easily volatilized.
Therefore, use of a solid acid catalyst as a substitute for a mineral acid catalyst such as sulfuric acid has been considered. A solid acid catalyst is useful as a catalyst for various chemical reactions because the above various steps after the reactions can be omitted or substantially simplified without apparatus corrosion, and various solid acids have been developed. Typical solid acids are inorganic compounds such as silica-alumina, crystalline aluminosilicate (synthetic zeolite), solid phosphoric acid and heteropoly acid.
For example, alkylation reactions such as for production of various alkyl aromatics and aralkyl compounds, and in addition, production of isoparaffin useful for production of high-octane gasoline are industrially very important reaction procedures, and an acid catalyst is used for the reactions. The above-described liquid strong acid such as sulfuric acid or hydrogen fluoride has been conventionally used. However, due to the above-described problems; the solid acid catalyst has recently been used.
In addition, polymerization reactions of olefins are important, for example, as methods for producing various polymers such as polystyrene and polybutene, and a solid acid catalyst is used also for the reactions.
However, the solid acid catalyst used for the conventional alkylation reaction or polymerization reaction of olefins has various problems. For example, examples of the solid acid catalyst used for alkylation reaction include synthetic zeolite catalysts and solid phosphoric acid catalysts. However, the synthetic zeolite catalysts are expensive. Also, the solid phosphoric acid catalysts are complicated in use, for example because the elution of phosphoric acid that is an active ingredient from the catalyst cannot be avoided, so a phosphoric acid component needs to be replenished as necessary. In addition, a strong acid ion-exchange resin, a polymer having a sulfonic acid group on the skeleton of a cross-linked polystyrene, is also known, but its range of use is limited due to problems such as the low heat resistance and expensiveness of the resin. The fluorine-substituted olefin polymer-based, very strong solid acid “NAFION” (a registered trademark of DuPont) having heat resistance and the like have been also developed, but they are too expensive to be used for industrial purposes.
On the other hand, Lewis acid-type catalysts such as aluminum chloride and boron trifluoride are generally used for the polymerization reaction of olefins. However, problems thereof include that these acid catalysts are highly corrosive to metal materials, and the acid catalyst is eluted into a reaction product, so a neutralization treatment of the reaction product is required.
Under these background, a sulfonic acid group-containing carbonaceous material obtained by carbonizing and sulfonating an organic substance such as an aromatic compound, petroleum heavy oil or sugars by heating has been developed. The sulfonic acid group-containing carbonaceous material has recently been attracting attention due to its high activities for various chemical reactions as a solid acid catalyst, excellent heat resistance, inexpensiveness and the like, and the evaluations thereof as a catalyst for esterification reaction of a fatty acid, hydrolysis reaction of an ester, alkylation reaction, hydration reaction of an olefin, and the like are being tried (Patent Document 1, Patent Document 2, Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3).
In addition, for example, in an alkylation reaction, in order to increase the activity as an acid catalyst, a method of heat-treating a composition of an organic substance and phosphoric acid to carbonize the organic substance and thereafter extracting the phosphoric acid is known (Non-Patent Document 4).
Furthermore, a catalyst obtained by further supporting on a support a solid acid catalyst obtained by carbonizing and sulfonating an organic substance is known (Non-Patent Document 3).    Patent Document 1: Japanese Patent Laid-Open No. 2004-238311    Patent Document 2: International Patent Publication No. WO 2005/029508 A1    Non-Patent Document 1: Domen et al., “Synthesis conditions and catalysis of carbon-based strong solid acids,” 85th Annual Meeting (Spring) of the Chemical Society of Japan (2005), 2B5-43    Non-Patent Document 2: Hara, M. et al. Nature, 438(10), 178, November (2005)    Non-Patent Document 3: Nara et al., PETROTECH, 29(6), 411 (2006)    Non-Patent Document 4: Ham et al., “Synthesis and characterization of carbon-based solid strong acid having large surface area,” 96th Meeting of the Catalysis Society of Japan (2005), 4E-21